Systems and methods for multiuser interleaving and modulation

ABSTRACT

Methods, systems, and apparatuses are disclosed for transmitting a plurality of bits to an access point (AP) and receiving constellation symbol from the AP. A constellation symbol may include a plurality of indications of bits. Each indication of the plurality of indications of bits may be associated with a respective wireless transmit/receive unit (WTRU) of a plurality of WTRUs. The plurality of indications of bits may include indications of bits modulated at a multi-user constellation bit division multiple access modulator (MU-CBDMAM).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Stage Entry under 35 U.S.C. § 371 ofPatent Cooperation Treaty Application No. PCT/US2015/053752, filed Oct.2, 2015, which claims the benefit of U.S. Provisional Patent ApplicationNo. 62/059,828, filed on Oct. 3, 2014. Each of Patent Cooperation TreatyApplication No. PCT/US2015/053752 and U.S. Provisional PatentApplication No. 62/059,828 is hereby incorporated by reference as iffully set forth herein.

BACKGROUND

In recent years, wireless devices such as smart phones, tabletcomputers, etc. have proliferated with the increased availability oflarger bandwidth wireless connections to networks such as the Internet.Such devices often use wireless local access network (WLAN) systems fornetwork access. WLAN systems may utilize multiple channel widths. Forexample, various channel widths are supported by systems described inInstitute of Electrical and Electronics Engineers (IEEE) standards802.11n, 802.11ac, 802.11af, and 802.11ah.

SUMMARY

Methods, systems, and apparatuses are disclosed for transmitting aplurality of bits to an access point (AP) and receiving constellationsymbol from the AP, where the constellation symbol may include aplurality of indications of, for example, a set of bits. A constellationsymbol may be associated with a uniform constellation or a non-uniformconstellation. Each indication may be associated with one or morewireless transmit/receive units (WTRUs). The indications of bits may begenerated by modulation at a multi-user constellation bit divisionmultiple access modulator (MU-CBDMAM). A MU-CBDMAM may operate as anopen loop MU-CBDMAM or a closed loop MU-CBDMAM, and may switch betweenthese methods of operation. Feedback may be transmitted by a WTRU in,e.g., a feedback control frame, to, e.g., an AP. Feedback may includeone or more of an acknowledgement (ACK), an indicator of channel stateinformation (CSI), and an indication of a signal-to-noise ratio (SNR).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a system diagram of an example communications system in whichthe disclosed subject matter may be implemented.

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A.

FIG. 1C is a system diagram of a non-limiting, exemplary Wi-Ficommunications system.

FIG. 2 is a block diagram of a non-limiting, exemplary transceiver.

FIG. 3 is a block diagram of a non-limiting, exemplary permutation.

FIG. 4 is a block diagram of a non-limiting, exemplary permutation.

FIG. 5 is a block diagram of a non-limiting, exemplary transceiver.

FIG. 6 is a block diagram of a non-limiting, exemplary permutation.

FIG. 7 is a block diagram illustrating a non-limiting, exemplary method.

FIG. 8 is a block diagram of a non-limiting, exemplary permutation.

FIG. 9 is a block diagram of a non-limiting, exemplary permutation.

FIG. 10 is a block diagram of non-limiting, exemplary modulators.

FIG. 11 is a block diagram of a non-limiting, exemplary transceiver.

FIG. 12 is a block diagram of a non-limiting, exemplary modulator.

FIG. 13 is a block diagram of a non-limiting, exemplary transceiver.

FIG. 14 is a block diagram of a non-limiting, exemplary transceiver.

FIG. 15 is a block diagram illustrating non-limiting, exemplary symbolsets.

FIG. 16 is a block diagram illustrating non-limiting, exemplary symbolsets.

FIG. 17 is a block diagram illustrating a non-limiting, exemplary statemachine.

FIG. 18 is a block diagram of a non-limiting, exemplary modulator.

FIG. 19 is a block diagram illustrating a non-limiting, exemplary signalflow.

FIG. 20 is a block diagram illustrating a non-limiting, exemplarymethod.

DETAILED DESCRIPTION

A detailed description of illustrative examples will now be describedwith reference to the various figures. Although this descriptionprovides a detailed example of possible implementations, it should benoted that the details are intended as illustrative examples only and inno way limit the scope of the application.

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed features may be implemented. For example, awireless network (e.g., a wireless network comprising one or morecomponents of the communications system 100) may be configured such thatbearers that extend beyond the wireless network (e.g., beyond a walledgarden associated with the wireless network) may be assigned QoScharacteristics.

The communications system 100 may be a multiple access system thatprovides content, such as voice, data, video, messaging, broadcast,etc., to multiple wireless users. The communications system 100 mayenable multiple wireless users to access such content through thesharing of system resources, including wireless bandwidth. For example,the communications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include at leastone wireless transmit/receive unit (WTRU), such as a plurality of WTRUs,for instance WTRUs 102 a, 102 b, 102 c, and 102 d, a radio accessnetwork (RAN) 104, a core network 106, a public switched telephonenetwork (PSTN) 108, the Internet 110, and other networks 112, though itshould be appreciated that the disclosed subject matter contemplates anynumber of WTRUs, base stations, networks, and/or network elements. Eachof the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the networks 112. By way of example, the base stations 114 a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a HomeNode B, a Home eNode B, a site controller, an access point (AP), awireless router, and the like. While the base stations 114 a, 114 b areeach depicted as a single element, it should be appreciated that thebase stations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one example, the base station 114 a may includethree transceivers, e.g., one for each sector of the cell. In anotherexample, the base station 114 a may employ multiple-input multipleoutput (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another example, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other examples, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (e.g.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneexample, the base station 114 b and the WTRUs 102 c, 102 d may implementa radio technology such as IEEE 802.11 to establish a wireless localarea network (WLAN). In another example, the base station 114 b and theWTRUs 102 c, 102 d may implement a radio technology such as IEEE 802.15to establish a wireless personal area network (WPAN). In yet anotherexample, the base station 114 b and the WTRUs 102 c, 102 d may utilize acellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.) toestablish a picocell or femtocell. As shown in FIG. 1A, the base station114 b may have a direct connection to the Internet 110. Thus, the basestation 114 b may not be required to access the Internet 110 via thecore network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it should be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B depicts an exemplary wireless transmit/receive unit, WTRU 102.WTRU 102 may be used in one or more of the communications systemsdescribed herein. As shown in FIG. 1B, the WTRU 102 may include aprocessor 118, a transceiver 120, a transmit/receive element 122, aspeaker/microphone 124, a keypad 126, a display/touchpad 128,non-removable memory 130, removable memory 132, a power source 134, aglobal positioning system (GPS) chipset 136, and other peripherals 138.It should be appreciated that the WTRU 102 may include anysub-combination of the foregoing elements while remaining consistentwith the disclosed subject matter.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it should be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one example, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another example, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherexample, the transmit/receive element 122 may be configured to transmitand receive both RF and light signals. It should be appreciated that thetransmit/receive element 122 may be configured to transmit and/orreceive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one example, the WTRU 102 may includetwo or more transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other examples, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It should be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anexample.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality, and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C illustrates exemplary wireless local area network (WLAN)devices. One or more of the devices may be used to implement one or moreof the features described herein. The WLAN may include, but is notlimited to, access point (AP) 102, station (STA) 110, and STA 112. STA110 and 112 may be associated with AP 102. The WLAN may be configured toimplement one or more protocols of the IEEE 802.11 communicationstandard, which may include a channel access scheme, such as DSSS, OFDM,OFDMA, etc. A WLAN may operate in a mode, e.g., an infrastructure mode,an ad-hoc mode, etc.

A WLAN operating in an infrastructure mode may comprise one or more APscommunicating with one or more associated STAs. An AP and STA(s)associated with the AP may comprise a basic service set (BSS). Forexample, AP 102, STA 110, and STA 112 may comprise BSS 122. An extendedservice set (ESS) may comprise one or more APs (with one or more BSSs)and STA(s) associated with the APs. An AP may have access to, and/orinterface to, distribution system (DS) 116, which may be wired and/orwireless and may carry traffic to and/or from the AP. Traffic to a STAin the WLAN originating from outside the WLAN may be received at an APin the WLAN, which may send the traffic to the STA in the WLAN. Trafficoriginating from a STA in the WLAN to a destination outside the WLAN,e.g., to server 118, may be sent to an AP in the WLAN, which may sendthe traffic to the destination, e.g., via DS 116 to network 114 to besent to server 118. Traffic between STAs within the WLAN may be sentthrough one or more APs. For example, a source STA (e.g., STA 110) mayhave traffic intended for a destination STA (e.g., STA 112). STA 110 maysend the traffic to AP 102, and, AP 102 may send the traffic to STA 112.

A WLAN may operate in an ad-hoc mode. The ad-hoc mode WLAN may bereferred to as independent basic service set (IBBS). In an ad-hoc modeWLAN, the STAs may communicate directly with each other (e.g., STA 110may communicate with STA 112 without such communication being routedthrough an AP).

IEEE 802.11 devices (e.g., IEEE 802.11 APs in a BSS) may use beaconframes to announce the existence of a WLAN network. An AP, such as AP102, may transmit a beacon on a channel, e.g., a fixed channel, such asa primary channel. A STA may use a channel, such as the primary channel,to establish a connection with an AP.

STA(s) and/or AP(s) may use a Carrier Sense Multiple Access withCollision Avoidance (CSMA/CA) channel access mechanism. In CSMA/CA a STAand/or an AP may sense the primary channel. For example, if a STA hasdata to send, the STA may sense the primary channel. If the primarychannel is detected to be busy, the STA may back off. For example, aWLAN or portion thereof may be configured so that one STA may transmitat a given time, e.g., in a given BSS. Channel access may include RTSand/or CTS signaling. For example, an exchange of a request to send(RTS) frame may be transmitted by a sending device and a clear to send(CTS) frame that may be sent by a receiving device. For example, if anAP has data to send to a STA, the AP may send an RTS frame to the STA.If the STA is ready to receive data, the STA may respond with a CTSframe. The CTS frame may include a time value that may alert other STAsto hold off from accessing the medium while the AP initiating the RTSmay transmit its data. On receiving the CTS frame from the STA, the APmay send the data to the STA.

A device may reserve spectrum via a network allocation vector (NAV)field. For example, in an IEEE 802.11 frame, the NAV field may be usedto reserve a channel for a time period. A STA that wants to transmitdata may set the NAV to the time for which it may expect to use thechannel. When a STA sets the NAV, the NAV may be set for an associatedWLAN or subset thereof (e.g., a BSS). Other STAs may count down the NAVto zero. When the counter reaches a value of zero, the NAV functionalitymay indicate to the other STA that the channel is now available.

The devices in a WLAN, such as an AP or STA, may include one or more ofthe following: a processor, a memory, a radio receiver and/ortransmitter (e.g., that may be combined in a transceiver), one or moreantennas (e.g., antennas 106 in FIG. 1C), etc. A processor function maycomprise one or more processors. For example, the processor may compriseone or more of: a general purpose processor, a special purpose processor(e.g., a baseband processor, a MAC processor, etc.), a digital signalprocessor (DSP), Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Array (FPGAs) circuits, any other type of integratedcircuit (IC), a state machine, and the like. The one or more processorsmay be integrated or not integrated with each other. The processor(e.g., the one or more processors or a subset thereof) may be integratedwith one or more other functions (e.g., other functions such as memory).The processor may perform signal coding, data processing, power control,input/output processing, modulation, demodulation, and/or any otherfunctionality that may enable the device to operate in a wirelessenvironment, such as the WLAN of FIG. 1C. The processor may beconfigured to execute processor executable code (e.g., instructions)including, for example, software, and/or firmware instructions. Forexample, the processor may be configured to execute computer readableinstructions included on one or more of the processor (e.g., a chipsetthat includes memory and a processor) or memory. Execution of theinstructions may cause the device to perform one or more of thefunctions described herein.

A device may include one or more antennas. The device may employmultiple input multiple output (MIMO) techniques. The one or moreantennas may receive a radio signal. The processor may receive the radiosignal, e.g., via the one or more antennas. The one or more antennas maytransmit a radio signal (e.g., based on a signal sent from theprocessor).

The device may have a memory that may include one or more devices forstoring programming and/or data, such as processor executable code orinstructions (e.g., software, firmware, etc.), electronic data,databases, or other digital information. The memory may include one ormore memory units. One or more memory units may be integrated with oneor more other functions (e.g., other functions included in the device,such as the processor). The memory may include a read-only memory (ROM)(e.g., erasable programmable read only memory (EPROM), electricallyerasable programmable read only memory (EEPROM), etc.), random accessmemory (RAM), magnetic disk storage media, optical storage media, flashmemory devices, and/or other non-transitory computer-readable media forstoring information. The memory may be coupled to the processor. Theprocessor may communicate with one or more entities of memory, e.g., viaa system bus, directly, etc.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have access to, and/or may interface with, aDistribution System (DS) and/or another type of wired and/or wirelessnetwork that may carry traffic in and out of a BSS. Traffic to STAs thatoriginates from outside the BSS may arrive through the AP and may bedelivered to one or more STAs. Traffic originating from one or more STAsand addressed to destinations outside the BSS may be sent to an AP to bedelivered to one or more respective destinations. Traffic between STAsthat communicate using a same WLAN in BSS mode may also be sent throughan AP where a source STA may send traffic to the AP and the AP maydeliver the traffic to a destination STA. Such traffic between STAswithin a same WLAN in BSS mode may be considered peer-to-peer traffic.Such peer-to-peer traffic may also be sent directly between a source STAand a destination STA using a direct link setup (DLS), such as an802.11e DLS or an 802.11z tunneled DLS (TDLS). A WLAN in Independent BSS(IBSS) mode may have no AP. STAs using a same WLAN in IBSS mode maycommunicate directly with each other. This mode of communication may bereferred to as an “ad-hoc” mode of communication.

In an 802.11 infrastructure mode of operation, an AP may transmit abeacon on a fixed channel that may be referred to as a primary channel.A primary channel may be 20 MHz wide and may be an operating channel ofa BSS. A primary channel may be used by STAs to establish a connectionwith an AP. A channel access mechanism in an 802.11 system may be amechanism that may be referred to as Carrier Sense Multiple Access withCollision Avoidance (CSMA/CA). In such a mode of operation, every STA,and any AP if present, may sense a primary channel. If a detectedprimary channel is determined to be busy, a detecting STA may back offor otherwise cease, at least temporarily, attempts to communicate usinga detected primary channel. In such examples, it may be that only oneSTA may transmit at any given time in a given WLAN in BSS mode.

In examples that implement some or all of the 802.11n specificationand/or the 802.11ac specification, devices implemented in such examplesmay operate in frequencies from 2 to 6 GHz. In other examples thatimplement some or all of the 802.11af and/or 802.11ah specification,devices implemented in such examples may operate in frequencies that areless than 1 GHz.

In 802.11n, High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication. In some such examples, this may be achieved by combininga primary 20 MHz channel with an adjacent 20 MHz channel to form a 40MHz wide channel.

In 802.11ac, Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz,80 MHz, and/or 160 MHz wide channels. 40 MHz and 80 MHz channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining eight contiguous 20 MHz channels or twonon-contiguous 80 MHz channels. Examples utilizing two 80 MHz channelsmay be referred to herein as an “80+80” configuration.

In an exemplary 80+80 configuration, transmitted data, after channelencoding, may be passed through a segment parser that may divide suchdata into two data streams. Inverse Fast Fourier Transform (IFFT) andtime domain processing may be performed on each stream separately. Theprocessed streams may be mapped on to two 80 MHz channels andtransmitted. On an entity receiving such streams, this process may bereversed and the combined data may be provided to the receiving entity'sMedia Access Control (MAC) layer.

A Request to Send/Clear to Send (RTS/CTS) Short Inter-Frame Space (SIFS)may be 16 μs and a guard interval (GI) may be 0.8 μs. Transmissions fromone or more nodes within 100 meters should remain within the GI, butbeyond 100 meters, the delay may be longer than 0.8 μs. At 1 kilometer,the delay may be over 6 μs.

In 802.11af and/or 802.11ah, channel operating bandwidths may be reducedas compared to 802.11n and 802.11ac channel operating bandwidths.802.11af may support 5 MHz, 10 MHz, and/or 20 MHz wide bands in TV WhiteSpace (TVWS). 802.11ah may support 1 MHz, 2 MHz, 4 MHz, 8 MHz, and/or 16MHz wide bands in non-TVWS. STAs in 802.11ah may be sensors with limitedcapabilities and may be limited to supporting 1 and/or 2 MHztransmission modes.

In WLAN systems that utilize multiple channel widths, such as systemsimplementing some or all of the 802.11n, 802.11ac, 802.11af, and/or802.11ah specifications, there may be a primary channel that may have abandwidth equal to a largest common operating bandwidth supported by allSTAs supported by the associated BSS. The bandwidth of the primarychannel may be limited by the STA that supports the smallest bandwidthoperating mode. In 802.11ah, the primary channel may be 1 or 2 MHz wideif there are STAs that only support 1 and 2 MHz modes, even though an APand/or other STAs in the BSS may support 4 MHz, 8 MHz, and/or 16 MHzoperating modes. Carrier sensing and/or navigation (NAV) setting(s) maydepend on the status of the primary channel. For example, if a primarychannel is busy (e.g., due to an STA supporting 1 and/or 2 MHz operatingmodes that is currently transmitting to the AP), then the availablefrequency bands may be considered busy even though a majority of theavailable frequency bands may remain idle and available. In 802.11ahand/or 802.11af, packets may be transmitted using a clock that may bedown-clocked (e.g., four or ten times as compared to the 802.11acspecification) to assist with this issue.

In the United States, available frequency bands that may be used by802.11ah may include frequency bands from 902 MHz to 928 MHz. In Korea,available frequency bands that may be used by 802.11ah may includefrequency bands from 917.5 MHz to 923.5 MHz. In Japan, availablefrequency bands that may be used by 802.11ah may include frequency bandsfrom 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11ahmay be 6 MHz to 26 MHz, depending on the country in which 802.11ah isimplemented.

802.11ac may utilize downlink Multi-User-Multiple-Input Multiple-Output(MU-MIMO) transmission to multiple STA's in a same symbol's time frame,such as during a downlink Orthogonal Frequency-Division Multiplexing(OFDM) symbol. Downlink MU-MIMO may also be used in 802.11ah. Each ofthe STA's involved in MU-MIMO transmission with an AP may be required touse the same channel or band, which may limit the operating bandwidth tothe smallest channel bandwidth that may be supported by the STA's thatmay be included in the MU-MIMO transmission with the AP.

802.11ac may form channels by combining up to eight contiguous 20 MHzchannels or two non-contiguous 80 MHz channels. Transmission proceduresin 802.11ac examples may use the entire allocated bandwidth fortransmission and reception. The IEEE 802.11ax specification, whenfinalized, may provide means for enhancing the performance of 802.11acexamples. IEEE 802.11ax may address spectral efficiency, areathroughput, and/or robustness to collisions and/or interference.Orthogonal Frequency-Division Multiplexing (OFDM) may be used in LongTerm Evolution (LTE) examples and/or Worldwide Interoperability forMicrowave Access (WiMAX) examples to address inefficiencies that may beintroduced by channel-based resource scheduling, for example as used by802.11ac examples.

A direct application of OFDM in the form of OrthogonalFrequency-Division Multiple Access (OFDMA) to wireless local areanetworks, such as WiFi, may introduce backward compatibility issues.Coordinated Orthogonal Block-based Resource Allocation (COBRA) may useOFDMA methods to resolve WiFi backward compatibility issues and theimplicit inefficiencies that may be caused by channel-based resourcescheduling. For example, COBRA may allow for transmissions overmultiple, smaller frequency-time resource units. Multiple users may beallocated to non-overlapping frequency-time resource unit(s) and may beenabled to transmit and receive simultaneously. A sub-channel may bedefined as a basic frequency resource unit that an AP may allocate to anSTA. For example, where backward compatibility with 802.11n/ac isdesired, a sub-channel may be defined as a 20 MHz channel.

COBRA may incorporate different methods to separate multiple users, suchas time domain multiplexing, frequency domain multiplexing, spatialdomain multiplexing, and/or polarization domain multiplexing. Forexample, COBRA may employ a scheme using one or more of OFDMAsub-channelization, SC-FDMA sub-channelization, and Filter-BankMulticarrier sub-channelization.

To assist in COBRA transmissions, methods for coverage range extension,grouping users, channel access, designing preambles for low overhead,beamforming and/or sounding, frequency and/or timing synchronization,and/or link adaptation may be used.

Timing and/or frequency synchronization algorithms may be used inembodiments, including COBRA embodiments. Multi-user and/or single usermultiple parallel channel access (MU-PCA and SU-PCA, respectively)schemes may also, or instead, be used in embodiments, including COBRAembodiments.

MU-PCA and SU-PCA embodiments may utilize parallel transmit and receivechannel access with symmetrical bandwidth, where down-link parallelchannel access (DL PCA) may be provided for multiple and/or singleusers, up-link parallel channel access (UL PCA) may be provided formultiple and/or single users, or combined DL PCA and UL PCA may beprovided for multiple and/or single users. In PCA embodiments (UL and/orDL), a frequency domain channel may be divided to smaller sub-channels.Each such sub-channel may have a same size or may differ in size fromother sub-channels. In such embodiments, a STA may be allocated to oneor more of such sub-channels. An exemplary system design may supportunequal modulation and coding schemes (MCS) and/or unequal transmitpower for SU-PCA and/or COBRA embodiments. In addition, or instead,physical layer (PHY) designs and procedures may be incorporated tosupport multi-user and/or single-user parallel channel access usingtransmit and/or receive with symmetrical bandwidth, while mixed MAC/PHYMU-PCA may also, or instead, be supported.

Multi-user and/or single-user parallel channel access transmit and/orreceive with asymmetrical bandwidth schemes may also be used, where MACdesigns and/or procedures may used for downlink, uplink, and/or combineduplink and downlink. PHY designs and/or procedures that may supportmulti-user and/or single-user parallel channel access using transmitand/or receive with asymmetrical bandwidth may also, or instead, beused.

Some of the 802.11 standard descriptions may describe systems thatfacilitate transmission to and/or reception from a single STA in onetime slot. Many transmission and/or reception designs known to thoseskilled in the art have been directed to single user transmissionscenarios. Methods may be implemented that utilize COBRA resourceallocation schemes for multiple simultaneous users. Transceiver methodsmay also, or instead, be implemented that utilize COBRA resourceallocation schemes for multiple simultaneous users.

Some of the 802.11 standard descriptions may also describe modulationschemes for single user transmission scenario. With the introduction ofa Multi-User (MU) feature, transmission design and/or modulation schemesfor multi-user scenarios may be used that may improve the transmissionefficiency, aggregate capacity, and/or spectrum efficiency.

A method may be used to improve the efficiency of multi-usercommunications that implements multi-user interleaving and/or modulationtechniques. Methods and procedures for the interleaving of multi-userbits may be used. For example, a multi-user interleaver may be used. Aprocedure for support of feedback information may also, or instead, beused to facilitate scheduling of multi-users' bits (e.g., selects and/orgroups) into a multi-user interleaver and/or modulator.

Multi-user interleaving may be implemented. Implementing support fordownlink MU-MIMO for one or more 802.11 standards may include changes tothe MAC layer. Modifications to the transceiver design and/or associatedprocedures may be used to support OFDMA-based multiple access schemes.

Support for sub-channelization may include changes to a sub-channelfrequency bandwidth and/or locations of sub-carriers. A sub-channel maybe defined as an allocation of a contiguous number of sub-carriers for aparticular data allocation. An AP, or another non-STA, that supportsOFDMA transmissions may assign one or more sub-channels to a STA.

Virtual interleaving may be implemented as described herein. N_(d) datasub-carriers may be used in one OFDM symbol. Each of the U sub-channelusers may be evenly allocated N_(u)=N_(d)/U non-overlapping datasub-carriers.

An interleaver designed for, e.g., a traditional single user 20 MHzsignal may be reused, e.g., to address multi-user scenarios. A diagramof exemplary transceiver 200 using virtual interleaver 230 isillustrated in FIG. 2. In transceiver 200, streams of bits associatedwith sub-channel users may be generated by bit generators 201, 202, 203,and 204, and encoded by encoders 211, 212, 213, and 214, respectively.These encoded bits may be processed by multi-user interleaving module280. Multi-user interleaving module 280 may multiplex such encoded bitsat grouping module 220. Grouping module 220 may generate one stream ofmultiplexed bits as an input to virtual interleaver 230. Virtualinterleaver 230 may have a size (e.g., a number of incoming/outgoingbits per block) of N_(int)=N_(d)N_(BPSCS).

Two permutations may be performed in virtual interleaver 230.Implemented together with sub-carrier allocation, a first permutationthat may be performed by virtual interleaver 230 may ensure adjacentcoded bits are mapped onto non-adjacent sub-carriers. A secondpermutation that may be performed by virtual interleaver 230 may ensurethat adjacent coded bits are mapped onto more and less significant bitsalternately. The interleaved bits may be processed by grouping module240 before modulation and sub-carrier mapping at multi-user CBDMAmodulator or separate modulators 250 and sub-carrier mapping module 260.Sub-carrier mapping module 260 may provide interleaved and mapped bitsto IFFT module 270.

Grouping module 240 may separate an interleaved bit stream received fromvirtual interleaver 230 into U substreams and modulate such substreamsseparately using discrete modulators. Grouping module 240 may insteadprovide the interleaved bit stream received from virtual interleaver 230to a constellation bit division multiple access modulator.

A virtual interleaver for multi-user implementations with equal MCS andequal information bit length for sub-channel users may be used.c_(n)=[c_(n)(0), c_(n)(1), . . . , c_(n)(N_(u)N_(BPSCS)−1)]^(T) maydenote coded bits from the output of an n-th encoder. These coded bitsmay be combined in a sequence c=[c₁ ^(T), c₂ ^(T), . . . , c_(U)^(T)]^(T). A first grouping may be a function ƒ(⋅) that may operate oninput sequence c. An output sequence may be denoted by x=[x₀, x₁, . . ., x_(N) _(CBPSS) ⁻¹]^(T). x may be sent to an interleaver for aninterleaving operation. The output bit of a first interleaverpermutation, w_(i), may be given by

$\begin{matrix}{{w_{i} = x_{k}}{i = {{U \cdot N_{BPSCS} \cdot \left( {k\;{mod}\; N_{u}} \right)} + \left\lfloor \frac{k}{N_{u}} \right\rfloor}}} & (1)\end{matrix}$where k=0, 1, . . . , N_(CBPSS)−1.

An output bit of a second interleaver permutation, y_(j), may be afunction of an output of a first interleaver permutation, w_(k), and maybe given by

$\begin{matrix}{{y_{j} = w_{k}}{j = {{s\left\lfloor \frac{k}{s} \right\rfloor} + {\left( {k + N_{CBPSS} - \left\lfloor \frac{N_{u} \cdot k}{N_{CBPSS}} \right\rfloor} \right)\;{mod}\; s}}}{{{{where}\mspace{14mu} k} = 0},1,\ldots\mspace{14mu},{N_{CBPSS} - 1},{{{and}\mspace{14mu} s} = {\max{\left\{ {1,\frac{N_{BPSCS}}{2}} \right\}.}}}}} & (2)\end{matrix}$

A virtual interleaver design may operate to generate an exemplary firstpermutation 300 shown in FIG. 3. In exemplary first permutation 300, anumber of total data sub-carriers N_(d)=52 and four sub-channel usersmay be considered, such that each sub-channel user has N_(u)=13sub-carriers. Modulation may be quadrature phase-shift keying (QPSK) andthus N_(BPSCS)=2. Each sub-channel user may be using a same, or equal,MCS. Bits from each sub-channel user may be indicated in FIG. 3 asC_(i), where i=1, 2, . . . , U, representing bits from an individualsub-channel user, and each user may be indicated in FIG. 3 as Ui, where,again, i=1, 2, . . . , U. An exemplary interleaving method maysequentially write the bits from one sub-channel user and then write thebits from the next sub-channel user and so on, as indicated in FIG. 3.The output bits of the first interleaver permutation may be read outcolumn-by-column from top to bottom, as indicated in FIG. 3.

A virtual interleaver may accommodate multiple users that utilizeunequal MCSs. Unequal MCSs may have the same code rate for eachsub-channel user and/or have different, or unequal, modulation orders.m_(u) may denote the multi-user index, m_(u)=1, 2, . . . , M_(u). Amulti-user may occupy one or more sub-channels. Where unequal MCSs ordifferent modulations for different sub-channel users are present, s andN_(BPSCS) may be a function of m_(u), and N_(CBPSS) may be a function ofM_(u). A virtual interleaver accommodating unequal MCSs (e.g., MCSshaving different modulations) may be described using c_(n)=[c_(n)(0),c_(n)(1), . . . , c_(n)(N_(u)N_(BPSCS)(m_(u))−1)]^(T) to denote thecoded bits from the output of the n-th encoder. The coded bits may becombined into a sequence c=[c₁ ^(T), c₂ ^(T), . . . , c_(U) ^(T)]^(T). Afirst grouping may be a function f(⋅) that may operate on input sequencec. An output sequence may be denoted by x=[x₀, x₁, . . . , x_(N)_(CBPSS) _((M) _(u) ⁾⁻¹]^(T). x may be sent to an interleaver forperformance of an interleaving operation. The output bit of a firstinterleaver permutation, w_(k), may be given by

$\begin{matrix}{{w_{i} = x_{k}}{i = {{\sum\limits_{m_{u} = 1}^{M_{u}}{{N_{BPSCS}\left( m_{u} \right)} \cdot \left( {k\;{mod}\; N_{u}} \right)}} + \left\lfloor \frac{k}{N_{u}} \right\rfloor}}} & (3)\end{matrix}$where k=0, 1, . . . , N_(CBPSS)(M_(u))−1 and N_(CBPSS)(M_(u))=N_(u)Σ_(m) _(u) ₌₁ ^(M) ^(u) N_(BPSCS)(m_(u)).

The output bit of a second interleaver permutation, y_(j), may be afunction of an output of a first interleaver permutation, w_(k), and maybe given by

$\begin{matrix}{{y_{j} = w_{k}}{j = {{{s\left( m_{u} \right)}\left\lfloor \frac{k}{s\left( m_{u} \right)} \right\rfloor} + {\left( {k + {N_{CBPSS}\left( M_{u} \right)} - \left\lfloor \frac{N_{u} \cdot k}{N_{CBPSS}\left( M_{u} \right)} \right\rfloor} \right)\;{mod}\;{s\left( m_{u} \right)}}}}{{{{where}\mspace{14mu} k} = 0},1,\ldots\mspace{14mu},{{N_{CBPSS}\left( M_{u} \right)} - 1},{{{and}\mspace{14mu}{s\left( m_{u} \right)}} = {\max{\left\{ {1,\frac{N_{BPSCS}\left( m_{u} \right)}{2}} \right\}.}}}}} & (4)\end{matrix}$

Exemplary permutation 400 that may be generated by a virtual interleaverfor a first permutation is illustrated in FIG. 4. A number of total datasub-carriers N_(d)=52. M_(u)=U=4 sub-channel users may be considered inthis example, so that each sub-channel user may have N_(u)=13sub-carriers. In this example, the modulation for user 1, user 3, anduser 4 (labeled U1, U3, and U4, respectively, in FIG. 4) may be QPSKwhile the modulation for user 2 (labeled U2 in FIG. 4) may be 16quadrature amplitude modulation (16QAM).N_(BPSCS)(m₁)=N_(BPSCS)(m₃)=N_(BPSCS)(m₄)=2, N_(BPSCS)(m₂)=4. In anexemplary interleaving method, the bits from one sub-channel user(where, in FIG. 4, bits from each sub-channel user may be indicated asC_(i), where i=1, 2, . . . , U) may be sequentially written and the bitsfrom the next sub-channel user may be written and so on as shown in FIG.4. The output bits of a first interleaver permutation may be read outcolumn-by-column from top to bottom as shown in FIG. 4.

Separate interleavers for multiple users may be used. In an OFDMA-basedmultiple access embodiment, a, e.g., 20 MHz channel may be considered asa baseline channel bandwidth. This baseline channel bandwidth may bepartitioned into four contiguous 5 MHz sub-channels. Each sub-carriergroup (SG) may be defined as a contiguous 5 MHz sub-channel (e.g., 16sub-carriers*312.5 KHz).

An AP may accommodate such sub-channel users (e.g., simultaneously) byutilizing OFDMA and may assign one SG per sub-channel user. Separateinterleaver designs may use each distinct interleaver to interleave(e.g., only interleave) coded bits of a single 5 MHz sub-channel user.Each sub-channel user may have its own dedicated interleaver.

Exemplary transceiver 500 is illustrated in the block diagram of FIG. 5.Transceiver 500 may use multi-user interleaving module 580, where eachof interleavers 521, 522, 523, and 524 may perform interleaving forcoded bits received from encoders 511, 512, 513, and 514, respectively.Encoders 511, 512, 513, and 514 may encode streams of bits received frombit generators 501, 502, 503, and 504, respectively. In transceiver 500,the streams of bits generated by bit generators 501, 502, 503, and 504may each be associated with a single sub-channel user.

Interleavers 521, 522, 523, and 524 may provide interleaved bits foreach sub-channel user to multi-user CBDMA modulator or separatemodulators 550, which may provide corresponding modulated bits tosub-carrier mapping module 560. Sub-carrier mapping module 560 mayprovide interleaved and mapped bits to IFFT module 570.

At least one criterion may be considered in a determination of whetherto use separate interleavers for each of multiple sub-channel users. Afirst interleaver permutation may be used to ensure that adjacent codedbits may be mapped onto non-adjacent sub-carriers, for example, becauseone sub-channel user may be allocated (e.g., only allocated) a portionof the total sub-carriers in one OFDMA symbol for the transmission ofits data. Sub-carrier allocation may also be considered in such anembodiment. A second interleaver permutation may be used to ensure thatadjacent coded bits are mapped alternatively onto less and moresignificant bits of the constellation. Sub-carrier allocation may alsobe considered in such an embodiment.

Utilizing separate interleavers, one or more same MCSs and/or one ormore same encoders may be used for associated sub-channel users. Forexample, the same MCSs and encoders may be used for four sub-channelusers. In such an embodiment, the four separate interleavers used foreach of the four sub-channel users may be identical.

A criteria of ensuring that adjacent coded bits may be mapped ontonon-adjacent sub-carriers may be satisfied by using a block permutationon the input bit sequence, which may operate in a column-wise input androw-wise output fashion. An interleaving bit size may be determined by

${N_{int} = {\frac{N_{d}}{U}N_{BPSCS}M}},$where N_(d) may be the total number of data sub-carriers in a, e.g., 20MHz channel bandwidth, U may be the number of sub-channel users,N_(BPSCS) may be the number of coded bits per sub-carrier, and M may bethe number of OFDM symbols associated with an interleaving block. Acriterion of ensuring that adjacent coded bits are mapped alternativelyonto less and more significant bits of a constellation may be satisfiedby circularly shifting the bit ordering every

$s = {\max\left\{ {1,\frac{N_{BPSCS}}{2}} \right\}\mspace{14mu}{{bits}.}}$

To perform a permutation for bits on a single sub-channel in a singleOFDMA symbol, an interleaver permutation that ensures that adjacentcoded bits are mapped onto non-adjacent sub-carriers may be implementedusing a permutation block column size is equal to a sub-carrier size.N_(d) data sub-carriers may be used in an OFDM symbol. Each of Usub-channel users may be allocated evenly such that N_(u)=N_(d)/Unon-overlapping data sub-carriers. In a permutation, an interleaving bitsize may be N_(int)=N_(u)N_(BPSCS), (e.g., where a single OFDMA symbolmay be used). A permutation block may have N_(u) columns and N_(BPSCS)rows. Input coded bits may be pushed into a permutation block row by rowand read out by a receiving device column by column. FIG. 6 illustratesexemplary permutation 600 representing an example of bits on a singlesub-channel in a single OFDMA symbol.

Bits of a single OFDMA symbol may be processed on a per sub-channel userbasis and may not have constraints on a total number of OFDMA symbolsper packet. An interleaving depth may be represented by N_(BPSCS), forexample as shown in FIG. 6. To ensure that adjacent coded bits aremapped onto non-adjacent sub-carriers, distributed sub-carrierallocation for sub-channel users may be used.

A permutation may be used for 16QAM and above and may not affect QPSKnegatively. With 16QAM and/or higher order modulations, every N_(BPSCS)bits may be mapped onto one symbol and every s=N_(BPSCS)/2 symbols maybe associated with either an imaginary or a real part of one symbol.There may be a set of s permutation matrices of size s. Such apermutation may be performed by alternately picking one permutationmatrix and applying it twice on two consecutive groups of s bits from aprevious permutation output. A set of permutation matrices may bedefined as integer powers of the cyclic permutation matrix P, e.g., {I,P, P², . . . , P ^(s−1) }, where I represents the identity matrix and Pmay be given by

$\begin{matrix}{P = {\begin{bmatrix}0 & 0 & \ldots & 0 & 1 \\1 & 0 & \ldots & 0 & 0 \\0 & \ddots & \ddots & \vdots & \vdots \\\vdots & \ddots & \ddots & 0 & 0 \\0 & \ldots & 0 & 1 & 0\end{bmatrix}.}} & (5)\end{matrix}$

Exemplary method 700 for generating such a permutation for 16QAM withs=3 is illustrated in FIG. 7, where each of the blocks of 710, 720, and130 may represent a particular bit. Any other MCS and/or value of s inany combination is contemplated. In method 700, as a non-limitingexample, three permutation matrices, which may represent I, P, P² wheres=3, may be used. A permutation may be performed by alternatelyselecting one permutation matrix and applying it twice on twoconsecutive groups of s bits from a previous permutation output. Each ofthe columns of bit representations shown in 710, 710, and 730 of FIG. 7may represent the initial set of bits for that block (on the right inthe respective block) and the bits after permutation (on the left in therespective block).

For example, at block 720, an identity matrix I=P⁰ may be selected andapplied twice on two consecutive groups of s bits (three bits in thisexample). At 722, one of matrices I, P, P² may be applied twice on anext two consecutive groups of s bits from an input sequence to apermutation output of 720 to generate the matrices of 730. This processmay continue, for example by selecting one of the matrices of 730 and,at 732, applying it twice on two consecutive groups of s bits from thepermutation output of 730 to generate additional matrices, continuingwith permutation 712 to generate matrices 710 and so forth.

One or more permutations for bits on a single sub-channel in multipleOFDMA symbols may be generated. A permutation may use an interleavingdepth equal to N_(BPSCS) and distributed sub-carrier allocation may beused. Coded bits associated with M OFDMA symbols may be aggregated asinputs to an interleaver. For example, each of the sub-channel users mayhave N_(u) data sub-carriers. An interleaving bit size may beN_(int)=N_(u)N_(BPSCS)M. A permutation block may have N_(u) columns andN_(BPSCS)M rows. An input and output rule may be the same as, or similarto, that used in permutations for bits on a single sub-channel in singleOFDMA symbol as described herein. An interleaving depth may beN_(BPSCS)M, which may support localized and/or distributed sub-carrierallocation.

Overhead may be introduced by fixing the number of OFDMA symbols for aninterleaving permutation because a number of coded bits in a packet maynot be equal or approximate to integer multiples of the interleaving bitsize. Splitting a coded bit sequence into chunks of size N_(u)N_(BPSCS)Mbits may result in a final chunk that may have very few data bits and/ora number of padded zeros.

Exemplary permutation 800 shown in FIG. 8 is an example of a permutationfor bits on a single sub-channel in multiple OFDMA symbols. Anotherpermutation for more and less significant bits may be the same as, orsimilar to, that shown in FIG. 8, and may handle more and lesssignificant bits similarly to permutations for bits on a singlesub-channel in a single OFDMA symbol as described herein.

A permutation for bits on a single sub-channel in a single OFDMA symbolmay be implemented using a permutation block column size that may beunequal to a sub-carrier size. In a permutation for bits on a singlesub-channel in a single OFDMA symbol where a permutation block columnsize may be equal to a sub-carrier size as described above, a number ofcolumns of a permutation block may be chosen to be N_(u). N_(u) may be asame number as a number of sub-carriers in one sub-channel. Given aninterleaving bit size of N_(u)N_(BPSCS), an interleaver depth may beN_(BPSCS). N_(u) may be a product of two integers, e.g., N_(u)=N_(col)T.In such an embodiment, a permutation block may have N_(col) columns andTN_(BPSCS) rows. An interleaver depth may be TN_(BPSCS). Input bits thatmay be associated with a single OFDMA symbol may be used and may avoidpotential additional overhead. Support for either or both localized anddistributed sub-carrier allocation may be provided. The distance insub-carrier mapping of adjacent coded bits may increase with anincreasing T when a localized sub-carrier allocation may be taken intoconsideration. Exemplary permutation 900 illustrated in FIG. 9 is anexample of such a permutation. A subsequent permutation may handle moreand less significant bits similarly to examples employing a permutationfor bits on a single sub-channel in a single OFDMA symbol as describedherein.

Multi-user modulation may be used for modulation in multi-userscenarios. A separate multi-user modulator may be used for eachmulti-user in such a scenario. Each such user may use its own separatemodulator and every constellation symbol (or modulated QAM symbol) mayconsist of bits from the same user. An example of a two-user modulatoris illustrated in FIG. 10 where the 16QAM constellation symbol for user1011 as modulated by modulator 1010 consists of the bits only from user1011 and where the 16QAM constellation symbol for user 1012 as modulatedby modulator 1020 consists of the bits only from user 1012.

A transceiver may employ separate multi-user modulators. FIG. 11 showsdiagram a block diagram of exemplary, non-limiting transceiver 1100 thatmay use separate modulators for multi-user scenarios. Transceiver 1100may use multi-user separate modulator module 1180, which may includemodulators 1151, 1152, 1153, and 1154 that each may be dedicated to anindividual user. Bits received from such users may be generated by bitgenerators 1101, 1102, 1103, and 1104, and encoded by encoders 1111,1112, 1113, and 1114, respectively. These encoded bits may be grouped bygrouping module 1120, but may instead not be processed by a groupingmodule. Grouped or otherwise encoded bits may be interleaved by virtualor other interleaver 1130, and may be grouped by grouping module 1140,or may instead not be processed by a grouping module after processing byinterleaver 1130.

Interleaved bits for each sub-channel user may be provided to modulators1151, 1152, 1153, and 1154 for individual modulation (e.g., separatemodulation for each user by modulators 1151, 1152, 1153, and 1154). Theresulting modulated bits for each user may be provided to sub-carriermapping module 1160, which may provide interleaved and mapped bits toIFFT module 1170.

In an exemplary embodiment similar to that exemplified by FIG. 11, fourusers may be served, each by one of bit generators 1101, 1102, 1103, and1104. The bit streams generated by bit generators 1101, 1102, 1103, and1104 for each user, which may be processed by encoders 1111, 1112, 1113,and 1114, grouping module 1120, virtual and/or other interleaver 1130,grouping module 1140, and/or modulators 1151, 1152, 1153, and 1154, maybe mapped to complex constellation points associated with a respectivestream corresponding to each user by sub-carrier mapping module 1160.

Interleaver 1130 may be a distinct, separate interleaver or a virtualinterleaver. Where interleaver 1130 is a separate, distinct interleaver,no grouping may be performed (e.g., grouping module 1120 and/or 1140 maynot be used) and each user's interleaved bits may be fed into separatemodulators 1151, 1152, 1153, and 1154. Where a virtual interleaver isused, the interleaved bits may be grouped with those of different users,for example by grouping module 1120 and/or grouping module 1140, andthen fed into a separate modulator for each user's bit, such as separatemodulators 1151, 1152, 1153, and 1154. Separate modulators 1151, 1152,1153, and 1154 may each be a BPSK, QPSK, 16-QAM, 64-QAM, and/or 256-QAMmodulator, or any other modulator.

In this an embodiment, a multi-user constellation bit division multipleaccess modulator (MU-CBDMAM) may be used that may support multi-usermodulation. Based on design criteria, an exemplary MU-CBDMAM may provideMU diversity gain, increase information access probability for multipleusers, improve frequency diversity, and/or provide flexibleequal/unequal error protection for different users.

A modulator may modulate bits from single user.

An MU-CBDMAM may generate one or more constellation symbols (and/or oneor more modulated QAM symbols) that may include bits that may be frommultiple users and/or different users. At least one of such symbols mayhave different weighting from the other symbols as a first bit of an Ior a Q branch may have more protection than a second bit of such an I orQ branch.

MU-CBDMAM modulation may be applied with uniform constellation (UC) orwith non-uniform constellation (NUC) to allow a constellation symbol tobe mapped using bits from multiple users. MU-CBDMAM modulation may use amultiple access (MA) scheme for multiple users that may be achieved at aconstellation level by allowing each constellation symbol to includebits from different users. MU-CBDMAM modulation may be open loop orclosed loop MU-CBDMAM modulation. Whether MU-CBDMAM modulation is openloop or closed loop may be based on a control signal that may bereferred to as a “user selector.” A value of a user selector may bebased on feedback received from one or more MU receivers. MU-CBDMAMmodulation may function as a modulation scheme that may be combined withsingle-carrier and/or multi-carrier transmission embodiments, such as,e.g., OFDM, that may provide multiple access capability for a multi-userembodiment.

An MU-CBDMAM may be used in COBRA implementations as well as otherimplementations. One or more constellation symbols, which may bemodulated constellation symbols, and/or 16QAM symbols (in an embodiment,modulated 16QAM symbols) may include bits that may be from multipleand/or different users. For example, exemplary two-user MU-CBDMAM 1210is illustrated in system 1200 shown in FIG. 12. Multi-user multiplexer(MU-MUX) 1220 of MU-CBDMAM 1210 may select bits from user A 1201 and/oruser B 1202 based on user selector signal 1240. This selection may beused to feed selected bits to constellation mapper 1230 mapper that maygenerate one more modulated symbols 1250, each of which may be 16QAMand/or QPSK symbols. Constellation mapper 1230 may, e.g., generateGray-coded constellation mappings. Other constellation mappings arecontemplated in the present disclosure.

Each of constellation symbols 1250 (which may be 16QAM and/or QPSKsymbols) may include bits that are from more than one user (e.g., bitsfrom user A 1201 and user B 1202). Constellation mapper 1230 may be asingle joint constellation mapper for MU-CBDMAM 1210 or M separateconstellation mappers, where M represents a number of users. Whereconstellation mapper 1230 is a joint constellation mapper, such a mappermay run N_BPSCS (e.g., a modulation order) times faster than ifconstellation mapper 1230 were a separate constellation mapper. In anexample such as that shown in FIG. 12, N_(BPSCS)=4 in a 16QAMembodiment. User selector signal 1240 may be a predefined signal or afeedback signal and may be based on whether MU-CBDMAM 1210 is an openloop MU-CBDMAM or a closed loop MU-CBDMAM.

Note that in this disclosure, an MU-CBDMAM may be independent of aninterleaver and may operate or otherwise be configured with any one ormore interleavers disclosed herein or any other one or moreinterleavers, and any combination thereof. All such embodiments arecontemplated as within the scope of this disclosure.

Exemplary transmitter 1300 of FIG. 13 may utilize MU-CBDMAM 1350. In theillustrated exemplary embodiment, four users 1391, 1392, 1393, and 1394may be associated with bit generators 1301, 1302, 1303, and 1304,respectively, and with encoders 1311, 1312, 1313, and 1314,respectively. Virtual interleaver 1330 may be used, as well as groupingmodules 1320 and/or 1340. Note that it is also contemplated that anembodiment may use one or neither of grouping modules 1320 and 1340.

A design of MU-CBDMAM 1350 may not be based on a design of interleaver1330, and other interleaver implementations are contemplated as withinthe scope of the instant disclosure. A design of MU-CBDMAM 1350 mayfunction with OFDM and/or OFDMA as described herein, but other channelaccess methods are contemplated as within the scope of the instantdisclosure.

Exemplary transceiver 1300 may be implemented for four users, althoughany number of users are contemplated as within the scope of the instantdisclosure. Illustrated discrete bit generators 1301, 1302, 1303, and1304 and encoders 1311, 1312, 1313, and 1314 may correspond to suchexemplary users. The respective bit streams for each user provided atthe output of interleaver 1330 (such bits may also be grouped bygrouping module 1320 and/or grouping module 1340) may be mapped tocomplex constellation points by MU-CBDMAM 1350 and mapped tosub-carriers by sub-carrier mapping module 1360. MU-CBDMAM 1350 mayselect bits from each of users 1391, 1392, 1393, and 1394 based on userselector signal 1380.

Interleaver 1330 may be a single virtual interleaver and interleavedbits from users 1391, 1392, 1393, and 1394 may be grouped and/orde-grouped, e.g., by grouping module 1320 and/or grouping module 1340and may be provided to MU-CBDMAM 1350. Design criteria used for animplementation of MU-CBDMAM 1350 may differ from criteria used inembodiments employing separate interleavers (e.g., exemplaryinterleavers 1431, 1432, 1433, and 1434 shown in FIG. 14). Interleaver1330 may map each user's bits alternatively onto more important levelsand less important levels.

Exemplary transceiver 1400 of FIG. 14 may utilize MU-CBDMAM 1450. In theillustrated exemplary embodiment, four users 1491, 1492, 1493, and 1494may be associated with bit generators 1401, 1402, 1403, and 1404,respectively, and with encoders 1411, 1412, 1413, and 1414,respectively. Separate, discrete interleavers 1431, 1432, 1433, and 1434may be used for each of users 1491, 1492, 1493, and 1494, respectively.

A design of MU-CBDMAM 1450 may not be based on a design of interleavers1431, 1432, 1433, and 1434, and other interleaver implementations arecontemplated as within the scope of the instant disclosure. A design ofMU-CBDMAM 1450 may function with OFDM and/or OFDMA as described herein,but other channel access methods are contemplated as within the scope ofthe instant disclosure.

Exemplary transceiver 1400 may be implemented for four users, althoughany number of users are contemplated as within the scope of the instantdisclosure. Illustrated discrete bit generators 1401, 1402, 1403, and1404 and encoders 1411, 1412, 1413, and 1414 may correspond to suchexemplary users. The respective bit streams for each user provided at anoutput of each of interleavers 1431, 1432, 1433, and 1434 may be mappedto complex constellation points by MU-CBDMAM 1450 and mapped tosub-carriers by sub-carrier mapping module 1460. MU-CBDMAM 1450 mayselect bits from each of users 1491, 1492, 1493, and 1494 based on userselector signal 1480. Interleaved and mapped bits may be provided toIFFT module 1470 by sub-carrier mapping module 1460.

Design criteria used for an implementation of MU-CBDMAM 1450 may differfrom criteria used in embodiments employing a virtual interleaver (e.g.,exemplary modulator 1350 shown in FIG. 13). Interleaver 1450 may mapeach user's bits alternatively onto more important levels and lessimportant levels.

Various means and methods of implementing an MU-CBDMAM modulator may beused in the disclosed embodiments. MU-CBDMAM modulators may have equalor unequal error probabilities. For example, S_(I,k) ¹ may represent aset of transmitted symbols that have a ‘1’ in the k^(th) bit of anI-branch while S_(I,k) ⁰ may represent a set of symbols that have a ‘0’in the k^(th) bit of I-branch. In this example, S_(Q,k) ⁰ and S_(Q,k) ¹may apply to a Q-branch. Referring now to diagrams 1500 and 1600 ofFIGS. 15 and 16, respectively, S_(I,1) may have less of a probability tobe an error than S_(I,2). S_(Q,1) may have less of a probability to bean error than S_(Q,2). A first bit of a constellation symbol of eitheran I or a Q branch may have more error protection than a second bit of aconstellation symbol of either the I or the Q branch. This aspect may beused to address multi-user simultaneous transmission in a fadingenvironment.

In a fading environment, different users may have different channelgains for a sub-carrier and/or a sub-channel. An MU-CBDMAM may provideequal error protection for different users based on the users'respective channel gains. This may allow for additional scheduling gainthat may be obtained for downlink (DL) OFDMA. This aspect of the instantdisclosure may be referred to as closed loop MU-CBDMAM due to the use ofchannel and/or channel-related information.

MU-CBDMAM may also, or instead, allow unequal error protection fordifferent users, e.g., for scheduling fairness and/or simplicity. Thisaspect of the instant disclosure may be referred to as open loopMU-CBDMAM as knowledge of channel information may not be available.

Operating as an open loop MU-CBDMAM or a closed loop MU-CBDMAM may bedynamically switched by an MU-CBDMAM based on knowledge and/or acondition of a channel, as shown in FIG. 17 illustrating MU-CBDMAM statemachine 1700 that may be implemented by an MU-CBDMAM modulator. In thisexample, an MU-CBDMAM may be operating in open loop MU-CBDMAM state1710. If it is determined at 1750 that there may exist a good channelcondition and/or that there may be no feedback available, the MU-CBDMAMimplementing exemplary state machine 1700 and operating in open loopMU-CBDMAM state 1710 may remain operating in open loop MU-CBDMAM state1710.

Where a poor channel condition is detected and/or where feedback isavailable to the MU-CBDMAM operating in open loop MU-CBDMAM state 1710,at 1730 an MU-CBDMAM implementing exemplary state machine 1700 may beginoperating in closed loop MU-CBDMAM state 1720. If, when operating inclosed loop MU-CBDMAM state 1720, an MU-CBDMAM detects a poor channelcondition and/or where feedback is available at 1760, such an MU-CBDMAMmay remain operating in closed loop MU-CBDMAM state 1720.

If, when operating in closed loop MU-CBDMAM state 1720, an MU-CBDMAMdetects a good channel condition and/or no feedback is available at1740, an MU-CBDMAM implementing exemplary state machine 1700 andoperating in closed loop MU-CBDMAM state 1720 may begin operating inopen loop MU-CBDMAM state 1710.

An open loop (OL) MU-CBDMAM may be used in implementations where unequalerror protection among users' transmissions may be desired (e.g., forscheduling fairness and/or simplicity). The controlling user selectorsignal may be one or any combination of a predefined user selectionpatterns (e.g., where each user of multi-users may be alternativelyselected to construct each constellation symbol), one or moreconstellation symbols constructed by a randomly selected user, and/or anaccess category (AC) or a quality of service (QoS) associated withdifferent users.

A closed loop (CL) MU-CBDMAM may be used in implementations where equalerror protection among users' transmissions may be desired (e.g., formulti-user diversity and/or scheduling gain). Because different usersmay have different channel gains for a respective sub-carrier orsub-channel, once an AP knows channel and/or channel-related informationfor each of the different users, the AP may assign different weighting,different bits, and/or different significance levels of constellationsymbol(s) to different users. A user with more fading for its channel(s)may obtain more error protection while a user with relatively lesschannel fading for its channel(s) may obtain less error protection when,for example, the AP maps the user with more channel fading onto a moresignificant level while mapping the user with less channel fading toless significant level.

The controlling user selector signal may be based on any one or anycombination of channel state information (CSI), channel qualityindicator (CQI), a signal to noise ratio (SNR), an acknowledgement(ACK), a negative acknowledgement (NACK), or any other data.

FIG. 18 illustrates exemplary system 1800 representing a system thatincludes CL MU-CBDMAM 1820. To provide equal error protection, CLMU-CBDMAM 1820 may select and map user 1's (“u1” in FIG. 18) bits 1840to a first bit of I and Q branches. For example, CL MU-CBDMAM 1820 maymap “I,1” if user 1 at 1860 is determined to have feedback with a lowSNR1, a low CSI1, a low CQI1, and/or a NACK. CL MU-CBDMAM 1820 mayselect and map user 2's bits (“u2” in FIG. 18) 1850 to a second bit of Iand Q branches. For example, CL MU-CBDMAM 1820 may map “Q,2” if user 2at 1870 is determined to have a high SNR2, a high CSI2, a high CQI2,and/or an ACK. In exemplary system 1800, 1810 may represent blocksrepresenting bits in a transceiver that may be provided to MU-CBDMAM1820. IFFT 1830 may represent an applied inverse fast Fourier transformthat may convert a frequency domain signal to a time domain. The blocksincluding 1810, 1820 and 1830 may be performed at a transmitter or atransceiver. H1 and H2 may represent fading channels, where Rx(u1) 1840and Rx(u2) 1850 may be receivers or transceivers at two users (u1 andu2, respectively) on such channels.

Different sub-channels and/or different sub-carriers may have differentlevels of fading. Different modulation schemes may be used for each ofsuch different sub-channels or sub-carriers. Such modulation schemes maybe used for symbol sets with differing quantities of MU-CBDMAMtransmissions.

Multi-user interleaving and multi-user modulation may be implementedtogether. While systems and methods that support multi-user interleavingin combination with multi-user modulation may be described herein, anyaspect of the disclosed subject matter may be implemented individuallyor in combination with any one or more of any other aspects disclosedherein. The features of any embodiment described herein are independentand may be considered as individual elements of the embodiment.

One or more signals transmitted by a transceiver may provide controlinformation to a receiver for de-interleaving and/or de-modulation. Inorder to support multi-user interleaving and/or multi-user modulation,e.g., in WiFi systems, a receiver may receive such control informationthat may indicate or otherwise allow the receiver to determine amulti-user interleaving and/or multi-user modulation scheme(s) used at atransceiver.

For example, information that may be determined by a receiver from atransceiver control signal may include a single bit that may indicate avirtual interleaver and/or separate interleavers by signaling a 1 or 0(or a 0 or 1). Another bit received by a receiver may indicate MU-CBDMAMmodulators or separate modulators by signaling a 1 or 0 (or 0 or 1). Areceiver may also determine, in some examples from a transceiver controlsignal, a number of users (sub-channel or otherwise) that may be groupedinto a virtual interleaver or an MU-CBDMAM.

A user selector control signal received by an MU-CBDMAM may bepredefined, and/or may be known by both a transmitter of such a signaland a receiver of such a signal associated with an MU-CBDMAM. Such acontrol signal may be implicitly and/or explicitly signaled between atransmitter and receiver.

A selection of an open loop MU-CBDMAM or a closed loop MU-CBDMAM may besignaled to one or more multi-users. Multi-users' bits order and/orgrouping may be provided to a virtual interleaver, e.g., using a controlsignal. An order of multi-users' bits, a bit selection, and/or a mappingof each multi-user's bits onto a constellation symbol may be signaled.Such information may be broadcast in a beacon, a short beacon, or anyother type of management, control, or extension frame(s). Suchinformation may be provided as part of a field, a subfield, and/or asubset of subfields of any information element (IE), or any combinationthereof. Such information may be transmitted as a part of any controland/or management frame, in any MAC and/or physical layer convergenceprotocol (PLCP) header, and/or as part of any combination thereof.

Multi-user virtual interleaving and/or MU-CBDMAM operation informationmay be signaled by a PLCP header and/or a MAC layer header. A legacyheader frame format for such headers may be used to, e.g., providebackwards compatibility. Reserved bit(s) and/or field(s) of such alegacy frame format may be reused to signal data representing multi-uservirtual interleaving and/or MU-CBDMAM operation information. Forexample, a reserved bit (1 bit) after a rate field in a legacy PLCPheader may be used to indicate whether support may be provided forvirtual interleaving. Such bits and/or fields may be used to indicatewhether support is provided for MU-CBDMAM. For example, a reserved bitin a PLCP header may be used to indicate if MU-CBDMAM may be supported.Virtual interleaver and/or MU-CBDMAM information may be signaled by oneor more of reserved bits in, for example, a PLCP service field (e.g.,bits 7 to 15) so that multiple selected stations may read, interpret,and/or derive virtual interleaver and/or MU-CBDMAM information to, forexample, facilitate de-interleaving and de-modulation.

A field or bit in a PLCP header or a MAC header (that may be a new orpreviously unused field and/or bit in a respective header) may be usedto signal multi-user virtual interleaving and/or MU-CBDMAM operationinformation. For example, a virtual interleaver field and/or anMU-CBDMAM field may be included in a signal (SIG) field of a PLCPheader. Such a SIG field may include a bitmap of an index of sub-channelusers grouped into a virtual interleaver or an MU-CBDMAM.

Multi-user virtual interleaving and/or MU-CBDMAM operation may besignaled by an IE. For example, a multi-user virtual interleavingelement and/or an MU-CBDMAM element may be included as an IE and/or asone or more fields or subfields of an IE that may be implemented as anexisting or new element, sub-element, or any management, control, orextension frame, or any combination thereof.

In an exemplary implementation, an element may signal multi-user virtualinterleaving and/or MU-CBDMAM operation(s) related information by addingone or more new fields and/or subfields to a capabilities IE and/or bycreating a new scrambling IE that may include some or all of possiblemulti-user virtual interleaving and/or MU-CBDMAM operation relatedinformation. The entirety or any portion of either or both of adisclosed element and disclosed fields and/or subfields may be presentin a beacon, an association request, an association response, areassociation request, a reassociation response, a probe request, aprobe response frame, or any combination thereof.

A user selector control signal may be signaled in a PLCP header, and maybe signaled in such a header using one or more signaling fields for anMU-CBDMAM modulator. For example, a user selector control signal may besignaled in a SIG-A signaling field, a SIG-B signaling field, or usingboth a SIG-A signaling field and a SIG-B signaling field of a PLCPheader. A NUC or UC may be implicitly signaled by using auto-detectionof IEEE 802.11 OFDMA packet classifications for an MU-CBDMAM modulator.

A feedback procedure may be employed to facilitate multi-userinterleaving and/or modulation. During an OFDMA multi-user transmissionopportunity (TXOP), an OFDMA AP may schedule a DL or an uplink (UL)transmission for one or more OFDMA STAs. One or more frames may betransmitted during the OFDMA TXOP to multiple OFDMA STAs. Anyprocedures, means, or methods set forth herein to support multi-userinterleaving and/or multi-user modulation may be implemented separatelyor in any combination. Such aspects are contemplated as independent ofother aspects and may be considered as individual aspects of thedisclosed embodiments.

An OFDMA-capable AP may acquire and initiate an OFDMA TXOP formulti-user interleaving and/or modulation using a beacon with accessparameters and/or a frame indicating access parameters. An OFDMAmulti-user multi-frame transmission may occur after a OFDMA TXOP isinitiated. The OFDMA AP may assign one or more sub-channels to differentsub-channel STAs and/or may schedule a same or different MCSs to varioussub-channel STAs. When “good” channel conditions are detected, some orall of the STAs may confirm such conditions using ACK frames that may betransmitted on the STAs respective assigned sub-channels as multiplesimultaneous ACKs and/or sequential ACKs.

An OFDMA AP may increase an MCS for some or all STAs, increase an MCSfor some or all STAs that may report a relatively higher CSI and/or SNR,increase an MCS for some or all STAs that may have a higher QoSrequirement, switch from CL MU-CBDMAM to OL MU-CBDMAM if less feedbacksignaling may be desired, increase a total number of multi-users to begrouped into a virtual interleaver, or any combination thereof (e.g., toimprove the system throughput).

Where poor channel conditions may be experienced, which may be indicatedby one or more STAs failing to report ACK back to the OFDMA AP, an APmay send data again to one or more STAs that did not report ACK untilthe retransmission time achieves a maximum predetermined value. Such anAP may choose to schedule a same sub-channel and a same multi-userinterleaving and/or modulation scheme for another STA. If there are noadditional OFDMA STAs waiting for transmission, the AP may choose to usea narrow band or allocate a STA with ACK feedback to the entirebandwidth.

Where poor channel conditions may be experienced, an AP may transmit toa different group of one or more OFDMA STAs other than the one or moreSTAs of the multi-user group that was the intended recipient group ofthe transmission. Multi-user interleaving and/or modulation operationsused by the AP may or may not be the same operations as those that mayhave been used in transmissions to the intended recipient multi-usergroup.

Where poor channel conditions may be experienced, a switch from OLMU-CBDMAM to CL MU-CBDMAM may be made. A “fail-to ACK” bit of one ormore STAs that may have failed to send an ACK may be mapped to a higherlevel of a constellation symbol. STAs associated with “succeed-to-ACK”bit(s) may be mapped to a lower level of a constellation symbol.

Where CL MU-CBDMAM was used for a previous transmission, an OFDMA AP maycontinue to use CL MU-CBDMAM but may switch the more and less importantlevels of a constellation symbol between a “fail-to-ACK” STA's bits anda “succeed-to-ACK” STA's bits. An AP may select bits from a“succeed-to-ACK” STA to replace those of a mostly “fail-to-ACK” STA. AnAP may replace a “fail-to-ACK” STA that has a low or lowest CSI and/orSNR with another STA that may not have been included in a previous or arecent transmission.

An AP may reduce a total number of sub-channel users grouped into avirtual interleaver relative to a previous transmission. For example, anAP may transmit to one STA using the entire available bandwidth and avirtual interleaver and MU-CBDMAM may fall back to an existing WiFisystem.

Where all STAs may fail to report an ACK, an AP may switch a currentTXOP to CSMA by transmitting an OFDMA TXOP end frame.

FIG. 19 shows a diagram of signal flow 1900 representing an exemplaryMU-CBDMAM TXOP process. AP 1980 may be in communication with STA 1990.At 1901, AP 1980 may initialize an MU-CBDMAM capability exchange betweenAP 1980 and STA 1990 by sending an MU-CBDMAM IE in a beacon to STA 1990.STA 1990 may respond by transmitting an association request at 1902 thatmay include an MU-CBDMAM IE. AP 1980 may respond with feedback that mayinclude an MU-CBDMAM IE in an association response at 1903.

At 1904, AP 1980 may send an MU-CBDMAM initiation control frame to STA1990 to reserve an MU-CBDMAM TXOP.

AP 1980 may send to STA 1990 an initial data transmission including afirst data frame based on OL MU-CBDMAM at 1905 if no channel conditionrelated information is available. Upon receipt of the initial datatransmission, STA 1990 may decode the transmission and feedback ACK,CSI, and/or SNR to AP 1980 by transmitting a first feedback controlframe to AP 1980 at 1906.

AP 1980 may generate one or more constellation symbols using anMU-CBDMAM state machine, for example as shown in FIG. 17, and may sendthe one or more constellation symbols to STA 1990 at 1907. At 1907, AP1980 may transmit MU-CBDMAM related data and a user selector signal in aSIG of a PLCP header. In response, STA 1990 may send a second feedbackcontrol frame that may include ACK, CSI, and/or SNR to AP 1980 at 1908.Any number of additional data and feedback frames may then be exchangedbetween AP 1980 and STA 1990. Note that one or any combination of ACK,CSI, and SNR may be used as feedback by an MU-CBDMAM state machine.

Upon completion of data transmissions at 1909, where AP 1980 maytransmit K^(th) MU-CBDMAM related data and/or a user selector signal toSTA 1990, for example in a SIG of a PLCP header, or if one or more otherconditions are met, (e.g., all STAs fail to report ACK to AP 1980), at1910 AP 1980 may send an MU-CBDMAM TXOP END frame to STA 1990 that mayswitch MU-CBDMAM TXOP to CSMA.

FIG. 20 illustrates a block diagram representing exemplary method 2000that may be performed in ACK-based MU-CBDMAM embodiments. At block 2010,after exchanging MU-CBDMAM capability information between an AP and atleast one STA, (e.g., using a beacon and association request/response),an AP may initiate and reserve an MU-CBDMAM TXOP by sending an MU-CBDMAMTXOP initiation control frame as an initial frame. At block 2012, the APmay begin an initial data transmission based on OL MU-CBDMAM if nochannel condition related information is available.

At block 2014, if all STAs successfully receive the first datatransmission and feedback ACKs to the AP, the AP may determine that achannel condition is good or adequate, and may return to block 2012 toconstruct constellation symbols using OL MU-CBDMAM.

If, at block 2014, not all STAs indicate that they each havesuccessfully received the first data transmission (e.g., not all STAshave fed back ACKs to the AP), the AP may determine that different STAs(or users) may be experiencing different channel conditions (e.g., oneor more STAs may be experiencing poor channel conditions while one ormore other STAs may be experiencing good channel conditions). Inresponse, at block 2016 the AP may construct constellation symbols usingCL MU-CBDMAM by using one or more of a variety of methods. An AP mayutilize MU diversity gain and increase an information access probabilityby mapping MU bits with and without ACK to less and more importantlevels or switch more and less important levels between the STAs withand without ACK for equal bit allocation. A number of bits allocated toeach user or to each user of a subset of users may be fixed.

At block 2016, the AP may attempt to obtain better frequency diversitygain by selecting more bits from a STA that provided an ACK to replace aSTA that failed to ACK or replace a fail-to-ACK STA with another STAthat was not transmitted to in the previous transmission.

At block 2018 the AP may determine whether all STAs have successfullyreceived the data transmission based on CL MU-CBDMAM by determiningwhether all the STAs have fed back ACKs to the AP. If so, the AP maycontinue constructing constellation symbols using CL MU-CBDMAM until allSTAs feedback ACKs, at which point the AP may construct constellationsymbols using OL MU-CBDMAM, returning to block 2012.

If it is determined at block 2018 that not all STAs reported ACK to theAP, the AP may determine, at block 2020, whether at least one ACK wasreceived. If so, the AP may perform one or more of the functions ofblock 2016. If no ACKs have been received at the AP, the AP may send anMU-CBDMAM TXOP END frame to switch MU-CBDMAM TXOP to CSMA.

Although the features and elements described this disclosure aredescribed using particular examples in particular combinations, eachfeature and element set forth herein may be used alone without the otherfeatures and/or elements of any of the disclosed examples. Each featureand element set forth herein may also be used with any one or more ofthe other features and/or elements of any of the disclosed examples.

The disclosed systems and methods may be used to facilitate OFDMA-basedmultiple access transmission and reception. While the instant disclosuremay refer to an IEEE 802.11 specification and/or a subset thereof, thedisclosed examples and description are not limited to systems, methods,or applications that implement, or are otherwise associated with, anyaspect of the IEEE 802.11 specification.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

What is claimed is:
 1. A method comprising: transmitting, from awireless transmit/receive unit (WTRU), a plurality of bits to an accesspoint (AP); receiving, at the WTRU, a constellation symbol from the AP,wherein the constellation symbol comprises a plurality of indications ofbits, wherein each indication of the plurality of indications of bits isassociated with a respective WTRU of a plurality of WTRUs, wherein eachindication of the plurality of indications of bits is associated with aweight, wherein a first weight associated with a first indication of theplurality of indications of bits is different than a second weightassociated with a second indication of the plurality of indications ofbits, and wherein the plurality of indications of bits comprisesindications of bits modulated at a multi-user constellation bit divisionmultiple access modulator (MU-CBDMAM).
 2. The method of claim 1, whereinthe plurality of indications of bits comprises indications of bitsmodulated at one of an open loop MU-CBDMAM or a closed loop MU-CBDMAM.3. The method of claim 1, wherein each indication of the plurality ofindications of bits is associated with a weighting that differs fromweightings associated with each other indication of the indications ofbits.
 4. The method of claim 1, wherein the constellation symbol isassociated with one of a uniform constellation or a non-uniformconstellation.
 5. The method of claim 1, further comprising receiving afirst MU-CBDMAM information element (IE) indicating a capability of theAP.
 6. The method of claim 5, wherein the first MU-CBDMAM IE iscomprised in a beacon.
 7. The method of claim 1, further comprisingtransmitting an association request to the AP comprising a secondMU-CBDMAM IE.
 8. The method of claim 1, further comprising receiving afirst data frame associated with one of an open loop MU-CBDMAM or aclosed loop MU-CBDMAM.
 9. The method of claim 1, further comprisingtransmitting a feedback control frame to the AP comprising thatcomprises at least one of an acknowledgement (ACK), an indicator ofchannel state information (CSI), and an indication of a signal-to-noiseratio (SNR).
 10. The method of claim 1, further comprising receiving anMU-CBDMAM transmission opportunity (TXOP) end frame.
 11. A wirelesstransmit/receive unit (WTRU) comprising: a transceiver configured totransmit a plurality of bits to an access point (AP); the transceiverfurther configured to receive a constellation symbol from the AP,wherein the constellation symbol comprises a plurality of indications ofbits, wherein each indication of the plurality of indications of bits isassociated with a respective WTRU of a plurality of WTRUs, wherein eachindication of the plurality of indications of bits is associated with aweight, wherein a first weight associated with a first indication of theplurality of indications of bits is different than a second weightassociated with a second indication of the plurality of indications ofbits, and wherein the plurality of indications of bits comprisesindications of bits modulated at a multi-user constellation bit divisionmultiple access modulator (MU-CBDMAM).
 12. The WTRU of claim 11, whereinthe plurality of indications of bits comprises indications of bitsmodulated at one of an open loop MU-CBDMAM or a closed loop MU-CBDMAM.13. The WTRU of claim 11, wherein each indication of the plurality ofindications of bits is associated with a weighting that differs fromweightings associated with each other indication of the indications ofbits.
 14. The WTRU of claim 11, wherein the constellation symbol isassociated with one of a uniform constellation or a non-uniformconstellation.
 15. The WTRU of claim 11, wherein the transceiver isfurther configured to receive a first MU-CBDMAM information element (IE)indicating a capability of the AP.
 16. The WTRU of claim 15, wherein thefirst MU-CBDMAM IE is comprised in a beacon.
 17. The WTRU of claim 11,wherein the transceiver is further configured to transmit an associationrequest to the AP comprising a second MU-CBDMAM IE.
 18. The WTRU ofclaim 11, wherein the transceiver is further configured to receive afirst data frame associated with one of an open loop MU-CBDMAM or aclosed loop MU-CBDMAM.
 19. The WTRU of claim 11, wherein the transceiveris further configured to transmit a feedback control frame to the APcomprising that comprises at least one of an acknowledgement (ACK), anindicator of channel state information (CSI), and an indication of asignal-to-noise ratio (SNR).
 20. The WTRU of claim 11, wherein thetransceiver is further configured to receive an MU-CBDMAM transmissionopportunity (TXOP) end frame.